by asdf
Thu Mar 5th, 2009 at 09:59:52 AM EST
Remember last year when there was an outcry because U.S. farmers had to temporarily store their grain on the ground because of a lack of railroad cars? Well, now with the economy in the tank, the railroads have the opposite problem: Nowhere to store the excess cars.
Also, in a sort of unrelated note, some interesting info about the reality of how hard it is to manage long heavy freight trains with their 19th century brake technology.
Under normal economic conditions, rail cars are "stored" on the main lines as they travel from place to place. But with reduced traffic, they are ending up in people's back yards.
Fort Collins is a busy enough train town that most cars parked in the city are eventually picked up, according to city and railroad officials. The city is luckier than other train towns, which are playing host to the more than 206,000 boxcars parked by the nation's five largest railroads. The number represents 30 percent of the nation's boxcars. An average boxcar is about 65 feet long; end-to-end, they would stretch from New York to Salt Lake City.
In December, Union Pacific Corp. parked a three-mile-long train of cars in Thornton south of 168th Avenue to just north of 136th Avenue. But residents revolted, and UP agreed to move the cars to an area north of Colo. 7 to just south of Weld County Road 6. They couldn't be moved until the city of Thornton removed asphalt that had been paved over the tracks near Weld 6, however.
http://www.fortcollinsnow.com/article/20090305
The air brakes on American railroads are surprisingly crude, basically unchanged from the original 19th century design. This makes it pretty challenging to actually drive a train through hilly terrain.
Sometime after 1 p.m., Train 762--two long black locomotives pulling 110 shiny aluminum cars, each heaped with over 90 000 kilograms of West Virginia coal--arrives at the Bluefield crest. The train, bound for the power plant at Hyco Lake, N.C., stretches nearly 2 km and weighs nearly 18 million kg.
The engineer, Jeff Hayslett, eases into his throttle to pull us over the hump, but it isn't long before he turns to the brakes. The Norfolk Southern, like most U.S. railroads, teaches engineers to control the train as much as possible with the locomotives' dynamic brakes, which slow the engines by reversing the electric current that powers their traction motors.
In practice, this means Hayslett uses the air brakes to set a base level of braking and the dynamic braking to modulate it. But here the air requires its own precision: If you're short a couple of pounds per square inch, the train might get away. (One pound per square inch is just under 7 kPa.) But if you're a couple of pounds over the mark, the train will stall, and you'll have to fully release the brakes (or "knock off the air") and then set them up again, probably before the reservoirs are fully charged. In the cab it's known as "pissing away your air."
"If you get your train set up the first time right, it means when you go down the mountain you ain't gotta fight the train," Hayslett explains. Otherwise "the train's gonna be working you instead of you working it."
He applies the dynamic brake, and we can feel a great number of gentle bumps as each hopper rolls into the one that preceded it. A few minutes later, with the train bunched up and the speed approaching 21 km/h, Hayslett grips a lever with two hands and reduces the brake pipe air by 8 pounds. His plan is to knock the air off at milepost N350, a flat spot in the grade where he'll have time to recharge the system before setting the brakes up again. Next he'll release the brakes again at Oakvale, W.Va., and then again several miles later, at the start of a very long stretch of flat running.
Then, after a long slog up a 16-km hill, we approach the entrance to the Merrimac Tunnel. Burrowing down for 1.5 km, with a grade of just over 1 percent, the tunnel presents an unusual braking challenge. Without braking, the train will gather momentum quickly. But Hayslett can't apply the air brakes while he's in the tunnel.
"Anytime you put the air on, you're subject for something to go wrong," explains Peters. Peters is thinking specifically of what's called a kicker, a sticking valve so sensitive to a reduction in brake-pipe pressure that it begins emergency braking and "kicks" the train swiftly to a halt. Braking miscues like this are called undesired emergencies, and they've grown more irksome for railroads in the last 20 years.
Traveling at 32 km/h, our train could stop in as little as 20 seconds if the brakes were applied at full force, Allran supposes. But then the forces acting on the train might be severe enough to cause it to derail.
http://www.spectrum.ieee.org/mar09/7927
